The disclosure relates to transparent glass-ceramic articles with improved mechanical strength, and precursor glasses and methods used to form such glass-ceramic articles, and more particularly to transparent glass-ceramic articles that include a nepheline crystalline phase and a transmittance of about 70% or greater, along the visible spectrum.
Sodium aluminosilicate glasses can be strengthened by ion exchange processes in which sodium cations present in the glasses are exchange for larger, potassium cations. Opaque nepheline-containing glass-ceramics can also be strengthened in the same manner.
Nepheline-containing glass-ceramics are typically nucleated by using a TiO2 nucleating agent. A significant amount of TiO2 nucleating agent is typically required to produce internal nucleation in nepheline-containing glass-ceramics (e.g., from about 5-10 wt %), which is an amount sufficient to cause a yellow or amber color in the parent glass (from which the glass-ceramic article is formed).
Accordingly, there is a need for transparent, colorless nepheline-containing glass-ceramic articles that exhibit improved mechanical strength and can be strengthened by known ion exchange methods.